/*
 * Copyright (c) 1996, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.util.zip;

import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;
import java.io.PushbackInputStream;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import static java.util.zip.ZipConstants64.*;
import static java.util.zip.ZipUtils.*;

/**
 * This class implements an input stream filter for reading files in the
 * ZIP file format. Includes support for both compressed and uncompressed
 * entries.
 *
 * @author David Connelly
 */
public class ZipInputStream extends InflaterInputStream implements ZipConstants {

  private ZipEntry entry;
  private int flag;
  private CRC32 crc = new CRC32();
  private long remaining;
  private byte[] tmpbuf = new byte[512];

  private static final int STORED = ZipEntry.STORED;
  private static final int DEFLATED = ZipEntry.DEFLATED;

  private boolean closed = false;
  // this flag is set to true after EOF has reached for
  // one entry
  private boolean entryEOF = false;

  private ZipCoder zc;

  /**
   * Check to make sure that this stream has not been closed
   */
  private void ensureOpen() throws IOException {
    if (closed) {
      throw new IOException("Stream closed");
    }
  }

  /**
   * Creates a new ZIP input stream.
   *
   * <p>The UTF-8 {@link java.nio.charset.Charset charset} is used to
   * decode the entry names.
   *
   * @param in the actual input stream
   */
  public ZipInputStream(InputStream in) {
    this(in, StandardCharsets.UTF_8);
  }

  /**
   * Creates a new ZIP input stream.
   *
   * @param in the actual input stream
   * @param charset The {@linkplain java.nio.charset.Charset charset} to be used to decode the ZIP
   * entry name (ignored if the <a href="package-summary.html#lang_encoding"> language encoding
   * bit</a> of the ZIP entry's general purpose bit flag is set).
   * @since 1.7
   */
  public ZipInputStream(InputStream in, Charset charset) {
    super(new PushbackInputStream(in, 512), new Inflater(true), 512);
    usesDefaultInflater = true;
    if (in == null) {
      throw new NullPointerException("in is null");
    }
    if (charset == null) {
      throw new NullPointerException("charset is null");
    }
    this.zc = ZipCoder.get(charset);
  }

  /**
   * Reads the next ZIP file entry and positions the stream at the
   * beginning of the entry data.
   *
   * @return the next ZIP file entry, or null if there are no more entries
   * @throws ZipException if a ZIP file error has occurred
   * @throws IOException if an I/O error has occurred
   */
  public ZipEntry getNextEntry() throws IOException {
    ensureOpen();
    if (entry != null) {
      closeEntry();
    }
    crc.reset();
    inf.reset();
    if ((entry = readLOC()) == null) {
      return null;
    }
    if (entry.method == STORED) {
      remaining = entry.size;
    }
    entryEOF = false;
    return entry;
  }

  /**
   * Closes the current ZIP entry and positions the stream for reading the
   * next entry.
   *
   * @throws ZipException if a ZIP file error has occurred
   * @throws IOException if an I/O error has occurred
   */
  public void closeEntry() throws IOException {
    ensureOpen();
    while (read(tmpbuf, 0, tmpbuf.length) != -1) {
      ;
    }
    entryEOF = true;
  }

  /**
   * Returns 0 after EOF has reached for the current entry data,
   * otherwise always return 1.
   * <p>
   * Programs should not count on this method to return the actual number
   * of bytes that could be read without blocking.
   *
   * @return 1 before EOF and 0 after EOF has reached for current entry.
   * @throws IOException if an I/O error occurs.
   */
  public int available() throws IOException {
    ensureOpen();
    if (entryEOF) {
      return 0;
    } else {
      return 1;
    }
  }

  /**
   * Reads from the current ZIP entry into an array of bytes.
   * If <code>len</code> is not zero, the method
   * blocks until some input is available; otherwise, no
   * bytes are read and <code>0</code> is returned.
   *
   * @param b the buffer into which the data is read
   * @param off the start offset in the destination array <code>b</code>
   * @param len the maximum number of bytes read
   * @return the actual number of bytes read, or -1 if the end of the entry is reached
   * @throws NullPointerException if <code>b</code> is <code>null</code>.
   * @throws IndexOutOfBoundsException if <code>off</code> is negative, <code>len</code> is
   * negative, or <code>len</code> is greater than <code>b.length - off</code>
   * @throws ZipException if a ZIP file error has occurred
   * @throws IOException if an I/O error has occurred
   */
  public int read(byte[] b, int off, int len) throws IOException {
    ensureOpen();
    if (off < 0 || len < 0 || off > b.length - len) {
      throw new IndexOutOfBoundsException();
    } else if (len == 0) {
      return 0;
    }

    if (entry == null) {
      return -1;
    }
    switch (entry.method) {
      case DEFLATED:
        len = super.read(b, off, len);
        if (len == -1) {
          readEnd(entry);
          entryEOF = true;
          entry = null;
        } else {
          crc.update(b, off, len);
        }
        return len;
      case STORED:
        if (remaining <= 0) {
          entryEOF = true;
          entry = null;
          return -1;
        }
        if (len > remaining) {
          len = (int) remaining;
        }
        len = in.read(b, off, len);
        if (len == -1) {
          throw new ZipException("unexpected EOF");
        }
        crc.update(b, off, len);
        remaining -= len;
        if (remaining == 0 && entry.crc != crc.getValue()) {
          throw new ZipException(
              "invalid entry CRC (expected 0x" + Long.toHexString(entry.crc) +
                  " but got 0x" + Long.toHexString(crc.getValue()) + ")");
        }
        return len;
      default:
        throw new ZipException("invalid compression method");
    }
  }

  /**
   * Skips specified number of bytes in the current ZIP entry.
   *
   * @param n the number of bytes to skip
   * @return the actual number of bytes skipped
   * @throws ZipException if a ZIP file error has occurred
   * @throws IOException if an I/O error has occurred
   * @throws IllegalArgumentException if {@code n < 0}
   */
  public long skip(long n) throws IOException {
    if (n < 0) {
      throw new IllegalArgumentException("negative skip length");
    }
    ensureOpen();
    int max = (int) Math.min(n, Integer.MAX_VALUE);
    int total = 0;
    while (total < max) {
      int len = max - total;
      if (len > tmpbuf.length) {
        len = tmpbuf.length;
      }
      len = read(tmpbuf, 0, len);
      if (len == -1) {
        entryEOF = true;
        break;
      }
      total += len;
    }
    return total;
  }

  /**
   * Closes this input stream and releases any system resources associated
   * with the stream.
   *
   * @throws IOException if an I/O error has occurred
   */
  public void close() throws IOException {
    if (!closed) {
      super.close();
      closed = true;
    }
  }

  private byte[] b = new byte[256];

  /*
   * Reads local file (LOC) header for next entry.
   */
  private ZipEntry readLOC() throws IOException {
    try {
      readFully(tmpbuf, 0, LOCHDR);
    } catch (EOFException e) {
      return null;
    }
    if (get32(tmpbuf, 0) != LOCSIG) {
      return null;
    }
    // get flag first, we need check EFS.
    flag = get16(tmpbuf, LOCFLG);
    // get the entry name and create the ZipEntry first
    int len = get16(tmpbuf, LOCNAM);
    int blen = b.length;
    if (len > blen) {
      do {
        blen = blen * 2;
      } while (len > blen);
      b = new byte[blen];
    }
    readFully(b, 0, len);
    // Force to use UTF-8 if the EFS bit is ON, even the cs is NOT UTF-8
    ZipEntry e = createZipEntry(((flag & EFS) != 0)
        ? zc.toStringUTF8(b, len)
        : zc.toString(b, len));
    // now get the remaining fields for the entry
    if ((flag & 1) == 1) {
      throw new ZipException("encrypted ZIP entry not supported");
    }
    e.method = get16(tmpbuf, LOCHOW);
    e.xdostime = get32(tmpbuf, LOCTIM);
    if ((flag & 8) == 8) {
            /* "Data Descriptor" present */
      if (e.method != DEFLATED) {
        throw new ZipException(
            "only DEFLATED entries can have EXT descriptor");
      }
    } else {
      e.crc = get32(tmpbuf, LOCCRC);
      e.csize = get32(tmpbuf, LOCSIZ);
      e.size = get32(tmpbuf, LOCLEN);
    }
    len = get16(tmpbuf, LOCEXT);
    if (len > 0) {
      byte[] extra = new byte[len];
      readFully(extra, 0, len);
      e.setExtra0(extra,
          e.csize == ZIP64_MAGICVAL || e.size == ZIP64_MAGICVAL);
    }
    return e;
  }

  /**
   * Creates a new <code>ZipEntry</code> object for the specified
   * entry name.
   *
   * @param name the ZIP file entry name
   * @return the ZipEntry just created
   */
  protected ZipEntry createZipEntry(String name) {
    return new ZipEntry(name);
  }

  /*
   * Reads end of deflated entry as well as EXT descriptor if present.
   */
  private void readEnd(ZipEntry e) throws IOException {
    int n = inf.getRemaining();
    if (n > 0) {
      ((PushbackInputStream) in).unread(buf, len - n, n);
    }
    if ((flag & 8) == 8) {
            /* "Data Descriptor" present */
      if (inf.getBytesWritten() > ZIP64_MAGICVAL ||
          inf.getBytesRead() > ZIP64_MAGICVAL) {
        // ZIP64 format
        readFully(tmpbuf, 0, ZIP64_EXTHDR);
        long sig = get32(tmpbuf, 0);
        if (sig != EXTSIG) { // no EXTSIG present
          e.crc = sig;
          e.csize = get64(tmpbuf, ZIP64_EXTSIZ - ZIP64_EXTCRC);
          e.size = get64(tmpbuf, ZIP64_EXTLEN - ZIP64_EXTCRC);
          ((PushbackInputStream) in).unread(
              tmpbuf, ZIP64_EXTHDR - ZIP64_EXTCRC - 1, ZIP64_EXTCRC);
        } else {
          e.crc = get32(tmpbuf, ZIP64_EXTCRC);
          e.csize = get64(tmpbuf, ZIP64_EXTSIZ);
          e.size = get64(tmpbuf, ZIP64_EXTLEN);
        }
      } else {
        readFully(tmpbuf, 0, EXTHDR);
        long sig = get32(tmpbuf, 0);
        if (sig != EXTSIG) { // no EXTSIG present
          e.crc = sig;
          e.csize = get32(tmpbuf, EXTSIZ - EXTCRC);
          e.size = get32(tmpbuf, EXTLEN - EXTCRC);
          ((PushbackInputStream) in).unread(
              tmpbuf, EXTHDR - EXTCRC - 1, EXTCRC);
        } else {
          e.crc = get32(tmpbuf, EXTCRC);
          e.csize = get32(tmpbuf, EXTSIZ);
          e.size = get32(tmpbuf, EXTLEN);
        }
      }
    }
    if (e.size != inf.getBytesWritten()) {
      throw new ZipException(
          "invalid entry size (expected " + e.size +
              " but got " + inf.getBytesWritten() + " bytes)");
    }
    if (e.csize != inf.getBytesRead()) {
      throw new ZipException(
          "invalid entry compressed size (expected " + e.csize +
              " but got " + inf.getBytesRead() + " bytes)");
    }
    if (e.crc != crc.getValue()) {
      throw new ZipException(
          "invalid entry CRC (expected 0x" + Long.toHexString(e.crc) +
              " but got 0x" + Long.toHexString(crc.getValue()) + ")");
    }
  }

  /*
   * Reads bytes, blocking until all bytes are read.
   */
  private void readFully(byte[] b, int off, int len) throws IOException {
    while (len > 0) {
      int n = in.read(b, off, len);
      if (n == -1) {
        throw new EOFException();
      }
      off += n;
      len -= n;
    }
  }

}
